Expandable orthopedic implant

ABSTRACT

An expandable intervertebral implant having an upper body portion, a lower body portion opposite the upper body portion, a wedge member connecting the upper body portion to the lower body portion, a nose member having a tapered distal end and a proximal end opposite the distal end, and an actuator disposed between the nose member and the wedge member, for translation of the wedge member along a longitudinal axis of the implant. A pin disposed in a center of the nose member connects to the actuator for centering the nose member with the actuator. Translation of the wedge member along the longitudinal axis of the implant displaces the upper body portion and the lower body portion away from each other, thereby expanding the intervertebral implant.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. Ser. No.16/135,734 filed Sep. 19, 2018, which is related and claims priority toU.S. Ser. No. 62/627,326, entitled Expandable Orthopedic Implant, filedFeb. 7, 2018, the entire contents of both applications are incorporatedherein by reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to implant devices for treating inparticular spinal disorders.

Description of the Related Art

Disorders of the spine often result in degeneration of the spinal discin the intervertebral space between the vertebral bodies. Spinaldisorders such as degenerative disc disease, disc herniation,osteoporosis, spondylolisthesis, stenosis, scoliosis and other curvatureabnormalities, kyphosis, tumor, and fracture may result from factorsincluding trauma, disease and degenerative conditions caused by injuryand aging. Spinal disorders typically result in symptoms including pain,nerve damage, and partial or complete loss of mobility. For example,after a disc collapse, severe pain and discomfort can occur due to thepressure exerted on nerves and the spinal column.

Conservative treatment can include non-operative treatment requiringpatients to adjust their lifestyles and submit to pain relievers and alevel of underlying pain. Operative treatment options include discremoval or the fusion or fixation of vertebrae together. Adjacentvertebra can be fixated or fused to each other using devices or bonegrafts. These may include, for example, screw and rod systems, interbodyspacers threaded fusion cages and the like.

Some fixation or fusion devices are attached to the vertebra from theposterior side. The device will protrude and result in additional length(i.e., needed to overlap the vertebrae) and additional hardware toseparately attach to each vertebrae. Fusion cages and allografts arecontained within the intervertebral space, but are inserted into theintervertebral space in the same dimensions as desired to occupy theintervertebral space. This requires that an opening sufficient to allowthe cage or graft to be inserted into the intervertebral space.

In the field of medical implant devices, implant devices are oftenimplanted into an intervertebral disc space in a collapsed state andexpanded to a desired height. Expansion has been accomplished bytranslating an expansion mechanism mated to the inferior and superiorendplates. In addition a large aperture at the proximal end of thedevice allows for post packing of bone graft material into the hollowinterior of the device, which is in communication with a fusion aperturein each of the superior and inferior endplates.

To achieve expansion and contraction the endplates are typically fixedin the longitudinal direction during translation of the expansionmechanism. An endplate retainer can be housed within the distal end ofthe housing mates with both the superior and inferior endplates andprohibits translation of the endplates, but allows for expansion.

U.S. Pat. No. 8,535,380 (the entire contents of which are incorporatedherein by reference) describes an implantable orthopedic stabilitydevice. The device had a contracted and an expanded configuration whichcould support and be fixed to either or both of adjacent vertebrae.

U.S. Pat. No. 8,894,712 (the entire contents of which are incorporatedherein by reference) describes an expandable intervertebral implant,including: a superior member configured to engage a superiorintervertebral body; an inferior member configured to engage an inferiorintervertebral body; and an expansion mechanism disposed between thesuperior member and the inferior member configured to selectively adjusta separation of the superior member from the inferior member.

U.S. Pat. No. 8,679,183 (the entire contents of which are incorporatedherein by reference) describes an expandable fusion device capable ofbeing installed inside an intervertebral disc space to maintain normaldisc spacing and restore spinal stability. In the '183 patent, thefusion device includes a body portion, a first endplate, and a secondendplate, the first and second endplates capable of being moved in adirection away from the body portion into an expanded configuration orcapable of being moved towards the body portion into an unexpandedconfiguration.

U.S. Pat. No. 9,320,610 (the entire contents of which are incorporatedherein by reference) describes an expandable implant including top andbottom plates having angled inner surface that interact with expansionmembers. The expansion members were situated on an actuator and includedat least one vertical projection for interacting with a recess in theplates.

U.S. Pat. No. 9,414,936 (the entire contents of which are incorporatedherein by reference) describes an intervertebral implant comprising afirst component and a second component. The second component included anactuator and a third component comprises a first ramp and a second rampaxially spaced apart from the first ramp. The third component comprisedrails including at least a portion of the ramps. The actuator wasengageable with the third component to effect axial translation suchthat the ramps engage at least one of the components between a firstconfiguration and a second configuration.

U.S. Pat. No. 9,526,627 (the entire contents of which are incorporatedherein by reference) describes an intervertebral implant to be implantedwithin an intervertebral space between endplates of adjacent vertebraduring use. The implant of the '627 patent included an upper memberhaving an inferior surface including an upper guide track and a superiorsurface to contact an endplate of an upper one of the adjacent vertebraduring use, a lower member having a superior surface including a lowerguide track and an inferior surface to contact an endplate of a lowerone of the adjacent vertebra during use, and an insert having a superiorsurface including an upper guide rail to engage the upper guide trackduring use and an inferior surface including a lower guide rail toengage the lower guide track during use.

U.S. Pat. No. 9,717,601 (the entire contents of which are incorporatedherein by reference) describes an implant including a first plate and asecond plate, a first wedge member and a second wedge member spaced fromthe first wedge member that couple the first and second plates together.In the '601 patent, the first and second wedge members were configuredto translate along the first and second plates from a first contractedconfiguration into a second separated configuration. The implantincluded an actuation member coupled to the first wedge member and thesecond wedge member. The actuation member was configured to move thefirst and second wedge members from the first contracted configurationinto the second separated configuration so that the first and secondplates separate from each other.

U.S. Pat. No. 9,717,605 (the entire contents of which are incorporatedherein by reference) describes a spinal fusion device that isexpandable. The spinal fusion device of the '605 patent features a topand bottom surface for engaging adjacent vertebrae, a hollow center forstacking of bone or bone growth material, and a slidable mechanism withgrooves for expanding or unexpanding the device.

U.S. Pat. No. 9,770,343 (the entire contents of which are incorporatedherein by reference) describes a spacer for separating bones of a joint,the spacer includes a frame having a longitudinal axis, and rampedsurfaces. In the '343 patent, an endplate configured to engage a bone ofthe joint had ramped surfaces mateable with the ramped surfaces of theframe. When the endplate was moved relative to the frame in a directionalong the longitudinal axis of the frame, the endplate was moved in adirection away from the frame to increase the height of the spacer.

U.S. Pat. No. 9,788,971 (the entire contents of which are incorporatedherein by reference) describes an expandable spinal fusion implantcomprising first and second endplates coupled to an expansion memberthat sits within a housing. The expansion member was translated by adrive mechanism, whereby translation of the expansion member by thedrive mechanism in a distal and proximal directions caused the distancebetween the endplates to increase and decrease, respectively.

SUMMARY OF THE INVENTION

In one embodiment, there is provided an expandable intervertebralimplant comprising an upper body portion, a lower body portion oppositethe upper body portion, a wedge member connecting the upper body portionto the lower body portion, a nose member having a tapered distal end anda proximal end opposite the distal end, the nose member slidablyconnected to the upper body portion and the lower body portion, anactuator disposed between the nose member and the wedge member, fortranslation of the wedge member along a longitudinal axis of theimplant, the actuator on a first side slidably connected the nose memberand on a second side connected to the wedge member, and a pin disposedin a center of the nose member and connecting to the actuator forcentering the nose member with the actuator. Translation of the wedgemember along the longitudinal axis of the implant displaces the upperbody portion and the lower body portion away from each other, therebyexpanding the intervertebral implant.

In one embodiment, there is provided an expandable intervertebralimplant comprising an upper body portion, a lower body portion oppositethe upper body portion, a nose member having a tapered distal end and aproximal end opposite the distal end, a wedge member connecting theupper body portion to the lower body portion, an actuator disposedbetween the nose member and the wedge member, for translation of thewedge member along a longitudinal axis of the implant, wherein a seriesof dovetail grooves connect the upper body portion, the lower bodyportion, the wedge member, and the nose member together, and translationof the wedge member along the longitudinal axis of the implant displacesthe upper body portion and the lower body portion away from each other,thereby expanding the intervertebral implant.

In one embodiment, there is provided an expandable intervertebralimplant comprising an upper body portion, a lower body portion oppositethe upper body portion, a nose member having a tapered distal end and aproximal end opposite the distal end, a wedge member connecting theupper body portion to the lower body portion, and comprising a firstwedge and a second wedge connected together, and an actuator disposedbetween the nose member and the wedge member, for translation of thewedge member along a longitudinal axis of the implant. A back side ofthe second wedge comprises the posterior end of the implant andcomprises an entire height of the implant. Translation of the wedgemember along the longitudinal axis of the implant displaces the upperbody portion and the lower body portion away from each other, therebyexpanding the intervertebral implant.

In one embodiment, there is provided an expandable intervertebralimplant comprising an upper body portion, a lower body portion oppositethe upper body portion, a nose member having a tapered distal end and aproximal end opposite the distal end, a wedge member connecting theupper body portion to the lower body portion, and comprising a firstwedge and a second wedge connected together, and an actuator disposedbetween the nose member and the wedge member, for translation of thewedge member along a longitudinal axis of the implant. The nose memberconnects to the upper body portion and the lower body portion by a pairof dovetail grooves on an external surface of the nose member.Translation of the wedge member along the longitudinal axis of theimplant displaces the upper body portion and the lower body portion awayfrom each other, thereby expanding the intervertebral implant.

In one embodiment, there is provided a system for stabilization ofvertebra, comprising the expandable implant described above; and aninsertion tool which turns the actuator described above and therebyexpands the implant.

In one embodiment, there is provided a method for stabilization ofvertebra, comprising attaching an insertion tool to the expandableimplant described above, inserting the expandable implant into anintervertebral space between adjacent vertebra; and expanding theexpandable implant.

It is to be understood that both the foregoing general description ofthe invention and the following detailed description are exemplary, butare not restrictive of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawing, wherein:

FIG. 1 is a perspective view of the implant device of the invention in acollapsed state;

FIG. 2 is a perspective view of the implant device of the invention inan expanded state;

FIG. 3 is a composite drawing showing a top down exploded view, afrontal, side, and rear view, and a bottom view of the implant device ofthe invention;

FIG. 4 is a schematic depiction of the individual components of theimplant device, showing the relative positions of those components;

FIG. 5 is a schematic depiction of the individual components of theimplant with attention on the dovetail groove assembly construction;

FIG. 6 is a schematic depicting a graft window in the implant;

FIG. 7 is a schematic depicting counter torque slots of the implant; and

FIG. 8 is a flowchart depicting a method of the invention forstabilization of vertebra.

DETAILED DESCRIPTION OF THE INVENTION

The implants of this invention are designed for spinal fusion proceduresto be used with autogenous bone graft in skeletally mature patients.While this invention is not so limited, the implants in one embodimentare intended for use at either one level or two contiguous levels in thelumbar spine, from L2 to S1, for the treatment of degenerative discdisease (DDD) with up to Grade I spondylolisthesis. DDD is definedherein as back pain of discogenic origin with degeneration of the discconfirmed by history and radiographic studies.

Expandable Implant

In one embodiment of the invention, the implants constitute expandableposterior lumbar interbody fusion (PLIF) implant products, although thisinvention is not limited to this specific target use.

With reference to FIGS. 1 and 2, FIG. 1 is a perspective view of theexpandable intervertebral implant 20 in a collapsed state. FIG. 2 is aperspective view of the expandable intervertebral implant 20 in anexpanded state. In one embodiment of the invention, the expandableintervertebral implant 20 has a nose member 1 having a tapered distalend and a proximal end opposite the distal end. A pin 2 (not shown inthis perspective) is disposed in a center of the nose member 1 andconnects to an actuator 3 (not shown in this perspective) for centeringthe nose member 1 with the actuator 3. The pin 2 maintains a position ofthe nose member 1 centered to the actuator 3 once the implant has beenassembled. An upper body portion 4, a wedge member 5, a lower bodyportion 6 opposite the upper body portion are shown in FIGS. 1 and 2.The wedge member 5 connects the upper body portion 4 to the lower bodyportion 5. Translation of the wedge member 5 along the longitudinal axisof the implant, e.g., by turning of the actuator 3, displaces the upperbody portion 4 and the lower body portion 6 away from the wedge member 5and away from each other, thereby expanding the intervertebral implantfor example in the cephalad direction denoted in FIG. 3.

FIG. 3 is a composite drawing showing a top down exploded view, afrontal, side, and rear view, and a bottom view of the implant of theinvention. As evident from FIG. 3, at least one of the upper bodyportion 4 and the lower body portion 6 comprises a corrugated surface 4a or 6 a for engaging with vertebra. The upper body portion 4 and thelower body portion 6 provide the load bearing surfaces for theintervertebral loads once implant 20 has been implanted and expanded. Asevident from FIG. 3, in one embodiment of the invention, the nose member5 is slidably connected to the upper body portion 4 and is slidablyconnected to the lower body portion 5 by the exterior dovetail grooves 1a, 1 b on nose member 1.

FIG. 4 is a schematic depiction of the individual components of theimplant 20, showing the relative positions of those components. Asevident from FIGS. 3 and 4, actuator 3 is disposed between nose member 1and wedge member 5. In one embodiment of the invention, the wedge membercomprises a first wedge 5 a and a second wedge 5 b connected together byone or more rails 5 c. With reference to FIG. 4, nose member 1 centersby way of pin 2 and retains the head of actuator 3 during expansion ofimplant 20.

In one embodiment of the invention, the actuator is disposed closer tothe nose member than to a posterior of the implant. In general, theinventive implant expands by utilizing actuator 3 which is connected bya threaded connection to wedge member 5, which contains for example apair of wedges 5 a, 5 b. When rotated, actuator 3 pulls the wedges (as aset) closer to the nose member 1 of implant 20 and, in turn, drives theupper and lower body portions 4, 6 away from the centerline of implant20. In other words, with actuator 3 being threadably connected to wedgemember 5, rotating actuator 3 translates the wedge member 5 along thelongitudinal axis of implant 20. Actuator 3 in one embodiment has athreaded outside surface 3 a with a head 3 b of the actuator, oppositethe wedge member 5, closer to the nose member 1 than to the posterior ofimplant 20. In one embodiment, actuator 3 and wedge member 5 haverespectively male and female threads to thereby advance wedge member 5when the actuator 3 is turned.

In one embodiment of the invention, the implants comprise low profileimplants with a minimal insertion height h for insertion into acollapsed intervertebral disc space. In this aspect of the invention,the height of the implant is that of the wedge member height, as seen inFIG. 3, which constitutes the maximum expansion distance. Accordingly,in this aspect of the invention, back side of the second wedge comprisesthe posterior end of implant 20 and comprises an entire height of theimplant. Once inserted (facilitated by its low profile in thisembodiment), implant 20 can expand for example in the cephalad-caudaldirection(s) to facilitate disc height restoration.

FIG. 5 is a schematic depiction of the individual components of theimplant 20 with attention on the dovetail groove assembly construction,As seen in FIG. 5, nose member 1 uses dovetail grooves 24 to slidablyconnect and guide expansion of the upper and lower body portions 4, 6and restrain any anterior-posterior movement of the upper and lower bodyportions 4, 6. Moreover, in one embodiment, dovetail grooves on thewedge member 5 hold and slidably connect the upper body portion 4 andthe lower body portion 6 to the wedge member 5. In another embodiment,dovetail grooves hold and slidably connect the upper body portion 4 andthe lower body portion 6 to the nose member 1. In another embodiment, aproximal end of nose member 1 comprises a pair of facing dovetailgrooves 1 a, 1 b comprising respective slots to receive therein the head3 a of the actuator 3.

In still another embodiment, a series of dovetail grooves connect thenose member 1, the upper body portion 4, the wedge member 5, and thelower body portion 6 together. In still another embodiment, the nosemember 1 slidably connects to the upper body portion 4 and the lowerbody portion 6 by a set of dovetail groove on an external surface of thenose member 1. In still another embodiment, a set of dovetail grooves onthe first wedge 5 a and the second wedge 5 b slidably connect the wedgemember 5 to the upper body portion 4 and/or to the lower body portion 6.In still another embodiment, a first set of dovetail grooves on the nosemember 1 fix the nose member 1 to the upper body portion 4 and the lowerbody portion 6, and a second set of dovetail grooves on the wedge member5 fix the upper body portion 4 and the lower body portion 6 to the wedgemember 5.

FIG. 6 is a schematic depicting a bone graft window 8 in implant 20. Asshown in FIG. 6, an opening in at least one of the upper body portion 4and the lower body portion 6 is provided for bone graft window 8. Thegraft window is also incorporated into wedge member 5. In one embodimentof the invention, by disposing the actuator mechanism toward the nose ofthe implant 20, a relatively large graft window 8 is provided for theimplant, and graft material can be injected into the implant 20 onceinserted and expanded in the patient. The relatively large graft windowfacilitates the bone growth and fusion process. In one embodiment, thegraft opening can range from 25% to 60% of the endplate area (e.g., thearea of the upper or lower body portion) depending on the footprint ofimplant 20. Regardless of the opening size and configuration, in oneembodiment, the implant device provides the capability to backfill bonegraft material into a graft window passing all the way though theimplant 20.

FIG. 7 is a schematic depicting counter torque slots 28 of implant 20and a through hole 30 in the posterior end of implant 20. The countertorque slots 28 permit an entirety of implant 20 to be rotated, that isimplant 20 as a unit is rotatable. The counter torque slots 28 preventthe implant from rotating, or tipping over, during expansion. Thecounter torque slots 28 stabilize the implant 20 against the torquebeing applied to the actuator during expansion. The through-hole 30grants access for the driver to the actuator. The through-hole 30 alsorepresents an opening for the insertion of bone graft material. In oneembodiment of the invention, the wedge member 5 comprises a first wedge5 a and a second wedge 5 b connected together by a pair of rails 5 c. Athrough-hole in the first wedge 5 a, a second through-hole in the secondwedge 5 b, and a spacing between the rails 5 c comprise a passageway foran insertion tool to connect to and turn actuator 3, and a passagewayfor bone graft material insertion.

In one embodiment of the invention, there is provided a system forstabilization of vertebra. This system utilizes any of the expandableimplants described above; and an insertion tool which turns the actuatordescribed above and thereby expands the implant. For example, actuator 3shown above can be rotated by a T-7 hexalobular driver fitting thecorresponding nut head 32 shown in FIG. 7. Accordingly, in oneembodiment, the insertion tool engages the counter torque slots to 1)provide a counter torque during expansion and 2) retain the implant 20to an inserter supplying bone graft material during the procedure. Thebone graft inserter can be cannulated. In one embodiment, theabove-noted T-7 driver is placed through the center of the bone graftinserter and engages the actuator. Bone graft material is then pushedthrough the inserter into implant 20 after implant 20 has been expanded.

In one embodiment, there is provided a method for stabilization ofvertebra. FIG. 8 is a flowchart depicting this method. This method at1001 attaches an insertion tool to any of the expandable implantsdescribed above. At 1003, the method inserts one (or more) of theexpandable implants into an intervertebral space between adjacentvertebra; and at 1005 expands the expandable implant.

After the expandable implant has been expanded, at 1007, the insertiontool may be removed (e.g., may be pulled from through hole 30 in theposterior end of implant 20. At 1009, bone graft material may then beinserted into the expanded implant filling the graft window 8 in situ.As noted above, the insertion of bone graft material promotes increasedfusion.

This invention is not limited to a specific type of bone graft material.In general, a variety of bone graft materials are known and suitable forthis invention. These typically comprise calcium phosphate-based orgel-based materials. Polymer-based bone graft substitutes containing (ornot containing) collagen can be used. Ceramic bone graft substitutes canbe used. In one embodiment, the implantable bone graft materialcomprises a composite of a ceramic and a polymer. The ceramic and thepolymer can be present at a weight ratio ranging from about 10:1 ceramicto polymer to about 2:1 ceramic to polymer. Alternatively, the weightratio of the ceramic to the polymer can range from about 2:1 (about 66%ceramic to about 33% polymer), from about 3:1 (about 75% ceramic toabout 25% polymer), from about 4:1 (about 80% ceramic to about 20%polymer), from about 9:1 (about 90% ceramic to about 10% polymer), fromabout 10:1 (about 99% ceramic to about 1% polymer). Other bone graftmaterials besides those specifically listed above can be used.

This invention is also not limited to the type of material that theimplant is made of. The implants of this invention can be made of anymaterial appropriate for human implantation and having the mechanicalproperties sufficient to be utilized for the intended purpose of spinalfusion, including various metals such as cobalt chrome, stainless steelor titanium including its alloys, various plastics including those whichare bio-absorbable, and various ceramics or combination sufficient forthe intended purpose. Further, the implants of this invention may bemade of a solid material, a mesh-like material, a porous material andmay comprise, wholly or in part, materials capable of directlyparticipating in the spinal fusion process, or be loaded with, composedof, treated of coated with chemical substances such as bone, morphogenicproteins, hydroxyapatite in any of its forms, and osteogenic proteins,to make them bioactive for the purpose of stimulating spinal fusion. Theimplants of this invention may be wholly or in part bioabsorbable. Othermaterials for the implant device besides those specifically listed abovecan be used.

This invention is also not limited to the methods by which the implantsare made. The individual components can be machined from solid stockpieces. Molding can be used to make the individual components. In thiscase, machining to final dimensions may or may not be in order. Thesurfaces once properly dimensioned can be coated with a variety ofbiocompatible coatings and/or surface treatments. Various coatingsinclude for example calcium phosphate ceramics, such as tricalciumphosphate (TCP) and hydroxyapatite (HA), and hydroxyapatite (a naturallyoccurring material in bone). Moreover, If the implant is not made ofbone, surfaces of the implant that contact bone may be treated topromote fusion of the implant to the bone. Treatment may include, but isnot limited to, applying a hydroxyapatite coating on contact surfaces,spraying a titanium plasma on contact surfaces, and/or texturing thecontact surfaces by scoring, peening, implanting particles in thesurfaces, or otherwise roughening the surfaces of the implant.

In some embodiments, any of the implants and instruments described above(such as the insertion tool) can be used with additional implants andinstruments. In some embodiments, the implants and instruments can beused with stabilization members, such as plates, screws, and rods. Inaddition, a multi-level construct can be formed, wherein any one or moreof the implants 20 described above can be used on one level, while asimilar or different implant (e.g., fusion or prosthetic) can be used ona different level.

Numerous modifications and variations of the present invention arepossible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described herein.

1. An expandable intervertebral implant comprising: an upper bodyportion; a lower body portion opposite the upper body portion; a wedgemember connecting the upper body portion to the lower body portion; anose member having a tapered distal end and a proximal end opposite thedistal end, the nose member slidably connected to the upper body portionand the lower body portion; an actuator having a connection for fittinga driver which engages the actuator where the connection is interior tothe wedge member and disposed closer to the nose member than a posteriorof the implant, for translation of the wedge member along a longitudinalaxis of the implant; and the actuator on a first side slidably connectedthe nose member and on a second side connected to the wedge memberwherein translation of the wedge member along the longitudinal axis ofthe implant displaces the upper body portion and the lower body portionaway from each other, thereby expanding the intervertebral implant. 2.The implant of claim 1, further comprising an opening in at least one ofthe upper body portion and the lower body portion configured to receivebone graft material.
 3. The implant of claim 1, wherein at least one ofthe upper body portion and the lower body portion comprises a corrugatedsurface for engaging with vertebra.
 4. The implant of claim 1, whereinthe actuator is threadably connected to the wedge member such thatrotating the actuator translates the wedge member along the longitudinalaxis.
 5. The implant of claim 1, wherein the wedge member comprises afirst wedge and a second wedge connected together by a rail.
 6. Theimplant of claim 1, wherein dovetail grooves on the wedge member holdand slidably connect the upper body portion and the lower body portionto the wedge member.
 7. The implant of claim 1, wherein dovetail grooveshold and slidably connect the upper body portion and the lower bodyportion to the nose member.
 8. The implant of claim 1, wherein aposterior-side end of the actuator is configured to connect with aninsertion tool for insertion of the implant between vertebrae.
 9. Theimplant of claim 1, wherein the actuator is disposed closer to the nosemember than a posterior end of the implant.
 10. The implant of claim 1,wherein a head of the actuator including the connection, opposite thewedge member, is closer to the nose member than a posterior end of theimplant.
 11. The implant of claim 1, wherein the actuator by turningadvances the wedge member toward the nose member and expands theimplant.
 12. The implant of claim 11, wherein the actuator and the wedgemember have respective male and female threads configured such that,when the actuator is turned, the wedge member is thereby advanced. 13.The implant of claim 1, further comprising: a first set of dovetailgrooves on the nose member which fix the nose member to the upper bodyportion and the lower body portion, and a second set of dovetail grooveson the wedge member which fix the upper body portion and the lower bodyportion to the wedge member.
 14. The implant of claim 1, wherein theproximal end of the nose member comprises a pair of facing dovetailgrooves configured to slidably connect and fix the nose member to theupper body portion and the lower body portion, and wherein a slot isconfigured to receive the first side of the actuator therein.
 15. Theimplant of claim 1, wherein the nose member slidably connects to theupper body portion and the lower body portion by a set of dovetailgrooves on an external surface of the nose member.
 16. The implant ofclaim 1, wherein the wedge member comprises a first wedge and a secondwedge, and wherein a set of dovetail grooves configured such that thefirst wedge and the second wedge slidably connect the wedge member tothe upper body portion.
 17. The implant of claim 1, wherein the wedgemember comprises a first wedge and a second wedge, and wherein a set ofdovetail grooves configured such that the first wedge and the secondwedge slidably connect the wedge member to the lower body portion. 18.The implant of claim 1, further comprising a pin disposed in a center ofthe nose member and connecting to the actuator for centering the nosemember with respect to the actuator.
 19. The implant of claim 18,wherein the pin is configured to maintain the nose member in a positionwhich is centered with respect to the actuator once the implant has beenassembled.